The invention relates to engines adapted to operate at low temperature and in particular to improvements in temperature differential fluid motors previously described by the author in U.S. Pat. No. 3,846,984 (application No. 464,823 filed Apr. 29, 1974).
Solar energy is available in practically unlimited quantities, is renewable, and pollution free. It, however, reaches the earth in a diffuse form and at relatively low temperatures. The conversion of solar thermal energy to electrical energy through existing conventional engines has been handicapped by the fact that the engines have been adapted to operate efficiently mainly at relatively high energy inputs. At low temperatures the conventional engines are relatively inefficient not only because of a low Carnot efficiency but also because of high operational losses, and low force outputs.
Past attempts to adapt solar energy to conventional engines have included utilization of means designed to increase solar energy inputs. For example, solar radiation concentrating means such as parabolic mirrors have been used to superheat water and water vapor for conventional steam engines. This has increased not only the temperature of solar energy but also its price and rendered the energy less competitive with alternate fossil and nuclear energy sources.
The present solar differential pressure engine is based upon the concept that it is cheaper to adapt the engine to the energy than to adapt the energy to the engine. The present report describes an engine which is especially adapted to operate at temperature ranges available in flat plate collector systems. In contrast to conventional engines the solar engine operates at low temperature inputs with relatively little operational losses, and can yield a relatively large force output.
The engine can be used to obtain practically unlimited amount of low cost electric energy through temperature differentials between flat plate collector systems and ambient air. Vast geographic areas of practically every climate are rendered suitable for the practical conversion of solar thermal energy to mechanical and electric energy. In torrid and temperate zones the engine can be used in roofs of small homes, in shore areas of oceans, lakes and rivers, and in dry desert areas. In frigid zones, the engine can be used to extract practically unlimited quantities of energy from natural large bodies of cold water through a temperature differential between the cold water and colder air.
The objectives of the present invention are:
1. To provide an engine which can convert solar thermal energy trapped in flat plate collector systems to mechanical and electrical energy.
2. To provide an engine which can exploit ambient temperature differentials for production of useful work.
3. To provide a small vapor or steam engine responsive to small pressures with relatively little operational losses.
Other objectives may become evident during the detailed description of the engine.